What is a safe ventilator volume based on weight and height?

From the Guidelines

The safe ventilator volume for adults is typically 6 ml/kg of ideal body weight (IBW), not actual weight, as recommended by the most recent and highest quality study 1. For a protective lung ventilation strategy, this volume is recommended, especially in patients with acute respiratory distress syndrome (ARDS). IBW can be calculated using formulas: for men, IBW (kg) = 50 + 2.3 × (height in inches - 60); for women, IBW (kg) = 45.5 + 2.3 × (height in inches - 60). For example, a 5'10" (70 inch) man would have an IBW of 73 kg, so his tidal volume would be approximately 438 ml. Using actual body weight can lead to ventilator-induced lung injury, especially in obese patients. Additionally, plateau pressures should be kept below 30 cmH2O to prevent barotrauma, as supported by studies such as 1 and 1. This approach is based on physiological principles that excessive stretching of lung tissue causes inflammation and damage. In children and neonates, lower tidal volumes of 4-6 ml/kg may be used, with adjustments based on clinical response, including oxygen saturation, chest rise, and blood gas measurements. Key considerations for mechanical ventilation in adult patients with ARDS include the use of lower tidal volumes and lower inspiratory pressures, as well as the potential benefits of prone positioning and higher positive end-expiratory pressure (PEEP), as discussed in studies such as 1, 1, and 1. Overall, the goal of mechanical ventilation is to support the patient's respiratory needs while minimizing the risk of lung injury and other complications.

Some key points to consider when determining a safe ventilator volume based on weight and height include:

• Using ideal body weight (IBW) rather than actual body weight to calculate tidal volume
• Targeting a tidal volume of 6 ml/kg IBW for adults with ARDS
• Keeping plateau pressures below 30 cmH2O to prevent barotrauma
• Considering the use of lower tidal volumes and higher PEEP in certain patients, such as those with severe ARDS
• Monitoring clinical response and adjusting ventilator settings as needed to optimize patient outcomes.

It's also important to note that the evidence supporting lower tidal volumes is not always applied, with a recent large international survey showing that tidal volume was kept at < 7 ml/kg PBW in only about 50% of patients with ARDS, as mentioned in 1. However, studies such as 1 provide guidance on the safe use of mechanical ventilation in patients with COVID-19, including the use of low tidal volumes and prone positioning. In summary, the safe ventilator volume for adults is typically 6 ml/kg of ideal body weight, with key considerations including the use of lower tidal volumes, lower inspiratory pressures, and higher PEEP, as well as the potential benefits of prone positioning, as supported by the most recent and highest quality studies 1.

From the Research

Safe Ventilator Volume Based on Weight and Height

To determine a safe ventilator volume based on weight and height, several factors must be considered, including the patient's predicted body weight (PBW) and the severity of their respiratory condition.

• The American Thoracic Society recommends using a tidal volume of 6 mL/kg of PBW for patients with acute respiratory distress syndrome (ARDS) 2.
• A study published in the New England Journal of Medicine found that ventilation with lower tidal volumes (6 mL/kg of PBW) resulted in decreased mortality and increased the number of days without ventilator use in patients with ARDS 2.
• Another study published in PLoS ONE found that visually estimating a patient's height to define tidal volume can lead to imprecise estimates and potentially harmful outcomes, highlighting the importance of measuring height accurately 3.
• The use of different PBW equations can also introduce variations in tidal volume settings, with some equations resulting in significantly different predicted body weights 4.
• A study published in Critical Care found that using a low-flow extracorporeal carbon dioxide removal system can facilitate ultra-protective ventilation with very low tidal volumes (4 mL/kg PBW) in patients with moderate ARDS 5.
• The implementation of a computerized clinical decision tool can also improve compliance with low tidal volume settings, with one study finding a significant decrease in the mean initial tidal volume set by clinicians after implementation of the tool 6.

Key Considerations

• Accurate measurement of patient height is crucial for determining safe ventilator volumes.
• The use of a standardized PBW equation, such as the NIH National Heart, Lung, and Blood Institute ARDS Network equation, can help minimize variations in tidal volume settings.
• Tidal volumes should be individualized based on patient characteristics, including PBW and the severity of their respiratory condition.
• The implementation of computerized clinical decision tools can help improve compliance with evidence-based ventilation strategies.